1.The characteristics of gusty winds due to two typhoons, No.17 and 19 of 1991, passed through northern Kyushu are comparatively reported using the measurement records at 24 meteorological stations in Kyushu area. Gust factors at many of the stations exceeded 2 in both typhoons. The turbulent intensities at the stations were estimated to be more than 30%.2.A new idea was discussed for improving aerodynamic instability of closed and open decks of PC cable- stayed bridge decks. The separation from a leeward separation point is controlled by a separated flow from a windward separation point. By using this method, non-streamlined shape deck can be chosen as the PC cable- stayed bridge girder and this method makes it possible to reduce the dead load of girder.3.The stability of bridge girders was examined, and every girder satisfied the required wind speed in their wind resistant design. For suppressing galloping of a steel pylon, a tuned mass damper has been installed near its top since erection. Rain-wind induced vibrations of cables were observed on a bridge during construction, and a pair of oil dampers has been installed near the lower end of every cable.2)PC斜張橋の最適主桁断面の選定PC斜張橋の最適主桁断面の選定に関し、2種類の2次元部分模型を製作し、一様流中で風洞実験を行った。その結果、PC斜張橋はその重量が大きいため、鋼斜張橋に比べ耐風性能は格段に良いが、やはり主桁断面形状として、予想される周囲流れのパターンを十分考慮して設計する必要がある。3)主桁断面の耐風性能を向上させるための空気力学的手法の開発橋梁断面に生じる空力弾性振動は、構造物の上流部隅角部からはがれた流れが流下するときに生じるはく離渦が引き起こす現象であるとの考えに立ち、フェアリング上に複数のはく離点を設けてはく離流の相互干渉作用を利用することによって空力弾性振動を制御する方法を見い出した。この方法はPC斜張橋の開断面、閉断面の両方に有効であり、死荷重を減少させ、空力安定性が増加した。